1. Field of the Invention
Embodiments of the invention relate to the field of optical communication, and more specifically, to timing recovery in optical transceivers.
2. Description of Related Art
High speed wave-division multiplexing (WDM) Single-Mode Fiber (SMF) optical communication links have extremely high bandwidths (i.e., fBW>10 THz for λ=1.5 μm) but suffer from low spectral efficiency, approximately from 0.2 bit per second per Hertz (b/s/Hz) to 0.8 b/s/Hz for Non-Return-To-Zero (NRZ) modulation used on each wavelength. This is due to nonlinearities in the fiber core (e.g. Self-Phase Modulation, Cross-Phase Modulation, etc.) as well as other impairments such as Polarization-Mode Dispersion (PMD). This results in expensive pre, post, and in-line optical dispersion compensation modules for high data rates (e.g., baud rates≧9.95 Gb/s) on each wavelength in a fiber link. Therefore, high speed SMF links without Dispersion Compensation modules (DCM) are limited to reaches of approximately from 80 km to 120 km.
Extending the reach of SMF high speed links to 320 Km and beyond with no pre, post, or in-line DCMs may face many problems. The low signal-to-noise ratio (SNR) due to the nonlinearities may lead to timing errors. The timing errors may in turn result in poor performance of signal detection.